Linux and open source articles and tutorials based on real world projects and deployments

How to Configure Cisco 881 Series Router with Cable modem and static IP

This tutorial will show how to configure Cisco 881 Series Router with Cable modem in bridged mode and static IP address. It will work with any model that has Fast Ethernet WAN interface. Simply what it means your WAN interface connects to Cable Modem with Regular Ethernet cat 5e or 6 patch cable.
The particular Cisco 881 model comes with following interfaces:

WAN Interface: 10/100-Mpbs Fast Ethernet

4 LAN Interfaces: 4-port 10/100-Mbps managed switch

In this example your company received static public IP address and we will use NAT to forward packets to internal computers. In our example WEB server is located on the internal network and all requests from outside NAT-ed to this server for http requests.
This setup will only work if you have static IP address from your ISP , if you use DHCP it will only work until your DHCP lease is renewed and then configuration will be broken.

When you first boot up your Cisco router, some basic configuration has already been performed. All of the LAN and WAN interfaces have been created, console and vty ports are configured, and the inside interface for Network Address Translation (NAT) has been assigned.